# Copyright 2014-2020 The PySCF Developers. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

'''
Moller-Plesset perturbation theory
'''

from pyscf import scf
from pyscf.mp import mp2
from pyscf.mp import dfmp2
from pyscf.mp import ump2
from pyscf.mp import gmp2

def MP2(mf, frozen=None, mo_coeff=None, mo_occ=None):
    if isinstance(mf, scf.uhf.UHF):
        return UMP2(mf, frozen, mo_coeff, mo_occ)
    elif isinstance(mf, scf.ghf.GHF):
        return GMP2(mf, frozen, mo_coeff, mo_occ)
    else:
        return RMP2(mf, frozen, mo_coeff, mo_occ)
MP2.__doc__ = mp2.MP2.__doc__

def RMP2(mf, frozen=None, mo_coeff=None, mo_occ=None):
    from pyscf import lib
    from pyscf.soscf import newton_ah

    if isinstance(mf, scf.uhf.UHF):
        raise RuntimeError('RMP2 cannot be used with UHF method.')
    elif isinstance(mf, scf.rohf.ROHF):
        lib.logger.warn(mf, 'RMP2 method does not support ROHF method. ROHF object '
                        'is converted to UHF object and UMP2 method is called.')
        return UMP2(mf, frozen, mo_coeff, mo_occ)

    if isinstance(mf, newton_ah._CIAH_SOSCF) or not isinstance(mf, scf.hf.RHF):
        mf = mf.to_rhf()

    if getattr(mf, 'with_df', None):
        return dfmp2.DFMP2(mf, frozen, mo_coeff, mo_occ)
    else:
        return mp2.RMP2(mf, frozen, mo_coeff, mo_occ)
RMP2.__doc__ = mp2.RMP2.__doc__

def UMP2(mf, frozen=None, mo_coeff=None, mo_occ=None):
    from pyscf.soscf import newton_ah

    if isinstance(mf, newton_ah._CIAH_SOSCF) or not isinstance(mf, scf.uhf.UHF):
        mf = mf.to_uhf()

    if getattr(mf, 'with_df', None):
        #raise NotImplementedError('DF-UMP2')
        return ump2.UMP2(mf, frozen, mo_coeff, mo_occ)
    else:
        return ump2.UMP2(mf, frozen, mo_coeff, mo_occ)
UMP2.__doc__ = ump2.UMP2.__doc__

def GMP2(mf, frozen=None, mo_coeff=None, mo_occ=None):
    from pyscf.soscf import newton_ah

    if isinstance(mf, newton_ah._CIAH_SOSCF) or not isinstance(mf, scf.ghf.GHF):
        mf = mf.to_ghf()

    if getattr(mf, 'with_df', None):
        raise NotImplementedError('DF-GMP2')
    else:
        return gmp2.GMP2(mf, frozen, mo_coeff, mo_occ)
GMP2.__doc__ = gmp2.GMP2.__doc__
